This invention relates generally to an apparatus and method for measuring the viscosity of liquids, and more particularly, an apparatus and methods for measuring the viscosity of the blood of a living being in-vivo and over a wide range of shears.
The importance of determining the viscosity of blood is well-known. Fibrogen, Viscosity and White Blood Cell Count Are Major Risk Factors for Ischemic Heart Disease, by Yarnell et al., Circulation, Vol. 83, No. 3, March 1991; Postprandial Changes in Plasma and Serum Viscosity and Plasma Lipids and Lipoproteins After an Acute Test Meal, by Tangney, et al., American Journal for Clinical Nutrition, 65:36-40, 1997; Studies of Plasma Viscosity in Primary Hyperlipoproteinaemia, by Leonhardt et al., Atherosclerosis 28,29-40, 1977; Effects of Lipoproteins on Plasma Viscosity, by Seplowitz, et al., Atherosclerosis 38, 89-95, 1981; Hyperviscosity Syndrome in a Hypercholesterolemic Patient with Primary Biliary Cirrhosis, Rosenson, et al., Gastroenterology, Vol. 98, No. 5, 1990; Blood Viscosity and Risk of Cardiovascular Events:the Edinburgh Artery Study, by Lowe et al., British Journal of Hematology, 96, 168-171, 1997; Blood Rheology Associated with Cardiovascular Risk Factors and Chronic Cardiovascular Diseases: Results of an Epidemiologic Cross-Sectional Study, by Koenig, et al., Angiology, The Journal of Vascular Diseases, November 1988; Importance of Blood Viscoelasticity in Arteriosclerosis, by Hell, et al., Angiology, The Journal of Vascular Diseases, June, 1989; Thermal Method for Continuous Blood-Velocity Measurements in Large Blood Vessels, and Cardiac-Output Determination, by Delanois, Medical and Biological Engineering, Vol. 11, No. 2, March 1973; Fluid Mechanics in Atherosclerosis, by Nerem, et al., Handbook of Bioengineering, Chapter 21, 1985.
Much effort has been made to develop apparatus and methods for determining the viscosity of blood. Theory and Design of Disposable Clinical Blood Viscometer, by Litt et al., Biorheology, 25, 697-712, 1988; Automated Measurement of Plasma Viscosity by Capillary Viscometer, by Cooke, et al., Journal of Clinical Pathology 41, 1213-1216, 1988; A Novel Computerized Viscometer/Rheometer by Jimenez and Kostic, Rev. Scientific Instruments 65, Vol 1, January 1994; A New Instrument for the Measurement of Plasma-Viscosity, by John Harkness, The Lancet, pp. 280-281, Aug. 10, 1963; Blood Viscosity and Raynaud""s Disease, by Pringle, et al., The Lancet, pp. 1086-1089, May 22, 1965; Measurement of Blood Viscosity Using a Conicylindrical Viscometer, by Walker et al., Medical and Biological Engineering, pp. 551-557, September 1976.
One reference, namely, The Goldman Algorithm Revisited: Prospective Evaluation of a Computer-Derived Algorithm Versus Unaided Physician Judgment in Suspected Acute Myocardial Infarction, by Qamar, et al., Am Heart J 138(4):705-709, 1999, discusses the use of the Goldman algorithm for providing an indicator to acute myocardial infarction. The Goldman algorithm basically utilizes facts from a patient""s history, physical examination and admission (emergency room) electrocardiogram to provide an AMI indicator.
In addition, there are a number of patents relating to blood viscosity measuring apparatus and methods. See for example, U.S. Pat. No. 3,342,063 (Smythe et al.); U.S. Pat. No. 3,720,097 (Kron); U.S. Pat. No. 3,999,538 (Philpot, Jr.); U.S. Pat. No. 4,083,363 (Philpot); U.S. Pat. No. 4,149,405 (Ringrose); U.S. Pat. No. 4,165,632 (Weber, et. al.); U.S. Pat. No. 4,517,830 (Gunn, deceased, et. al.); U.S. Pat. No. 4,519,239 (Kiesewetter, et. al.); U.S. Pat. No. 4,554,821 (Kiesewetter, et. al.); U.S. Pat. No. 4,858,127 (Kron, et. al.); U.S. Pat. No. 4,884,577 (Merrill); U.S. Pat. No. 4,947,678 (Hori et al.); U.S. Pat. No. 5,181,415 (Esvan et al.); U.S. Pat. No. 5,257,529 (Taniguchi et al.); U.S. Pat. No. 5,271,398 (Schlain et al.); and U.S. Pat. No. 5,447,440 (Davis, et. al.).
The Smythe ""063 patent discloses an apparatus for measuring the viscosity of a blood sample based on the pressure detected in a conduit containing the blood sample. The Kron ""097 patent discloses a method and apparatus for determining the blood viscosity using a flowmeter, a pressure source and a pressure transducer. The Philpot ""538 patent discloses a method of determining blood viscosity by withdrawing blood from the vein at a constant pressure for a predetermined time period and from the volume of blood withdrawn. The Philpot ""363 patent discloses an apparatus for determining blood viscosity using a hollow needle, a means for withdrawing and collecting blood from the vein via the hollow needle, a negative pressure measuring device and a timing device. The Ringrose ""405 patent discloses a method for measuring the viscosity of blood by placing a sample of it on a support and directing a beam of light through the sample and then detecting the reflected light while vibrating the support at a given frequency and amplitude. The Weber ""632 patent discloses a method and apparatus for determining the fluidity of blood by drawing the blood through a capillary tube measuring cell into a reservoir and then returning the blood back through the tube at a constant flow velocity and with the pressure difference between the ends of the capillary tube being directly related to the blood viscosity. The Gunn ""830 patent discloses an apparatus for determining blood viscosity that utilizes a transparent hollow tube, a needle at one end, a plunger at the other end for creating a vacuum to extract a predetermined amount and an apertured weight member that is movable within the tube and is movable by gravity at a rate that is a function of the viscosity of the blood. The Kiesewetter ""239 patent discloses an apparatus for determining the flow shear stress of suspensions, principally blood, using a measuring chamber comprised of a passage configuration that simulates the natural microcirculation of capillary passages in a being. The Kiesewetter ""821 patent discloses another apparatus for determining the viscosity of fluids, particularly blood, that includes the use of two parallel branches of a flow loop in combination with a flow rate measuring device for measuring the flow in one of the branches for determining the blood viscosity. The Kron ""127 patent discloses an apparatus and method for determining blood viscosity of a blood sample over a wide range of shear rates. The Merrill ""577 patent discloses an apparatus and method for determining the blood viscosity of a blood sample using a hollow column in fluid communication with a chamber containing a porous bed and means for measuring the blood flow rate within the column. The Hori ""678 patent discloses a method for measurement of the viscosity change in blood by disposing a temperature sensor in the blood flow and stimulating the blood so as to cause a viscosity change. The Esvan ""415 patent discloses an apparatus that detects the change in viscosity of a blood sample based on the relative slip of a drive element and a driven element, which holds the blood sample, that are rotated. The Taniguchi ""529 patent discloses a method and apparatus for determining the viscosity of liquids, e.g., a blood sample, utilizing a pair of vertically-aligned tubes coupled together via fine tubes while using a pressure sensor to measure the change of an internal tube pressure with the passage of time and the change of flow rate of the blood. The Bedingham ""328 patent discloses an intravascular blood parameter sensing system that uses a catheter and probe having a plurality of sensors (e.g., an O2 sensor, CO2 sensor, etc.) for measuring particular blood parameters in vivo. The Schlain ""398 patent discloses a intra-vessel method and apparatus for detecting undesirable wall effect on blood parameter sensors and for moving such sensors to reduce or eliminate the wall effect. The Davis ""440 patent discloses an apparatus for conducting a variety of assays that are responsive to a change in the viscosity of a sample fluid, e.g., blood.
Viscosity measuring methods and devices for fluids in general are well-known. See for example, U.S. Pat. No.: 1,810,992 (Dallwitz-Wegner); U.S. Pat. No. 2,343,061 (Irany); U.S. Pat. No. 2,696,734 (Brunstrum et al.); U.S. Pat. No. 2,700,891 (Shafer); U.S. Pat. No. 2,934,944 (Eolkin); U.S. Pat. No. 3,071,961 (Heigl et al.); U.S. Pat. No. 3,116,630 (Piros); U.S. Pat. No. 3,137,161 (Lewis et al.); U.S. Pat. No. 3,138,950 (Welty et al.); U.S. Pat. No. 3,277,694 (Cannon et al.); U.S. Pat. No. 3,286,511 (Harkness); U.S. Pat. No. 3,435,665 (Tzentis); U.S. Pat. No. 3,520,179 (Reed); U.S. Pat. No. 3,604,247 (Gramain et al.); U.S. Pat. No. 3,666,999 (Moreland, Jr. et al.); U.S. Pat. No. 3,680,362 (Geerdes et al.); U.S. Pat. No. 3,699,804 (Gassmann et al.); U.S. Pat. No. 3,713,328 (Aritomi); U.S. Pat. No. 3,782,173 (Van Vessem et al.); U.S. Pat. No. 3,864,962 (Stark et al.); U.S. Pat. No. 3,908,441 (Virloget); U.S. Pat. No. 3,952,577 (Hayes et al.); U.S. Pat. No. 3,990,295 (Renovanz et al.); U.S. Pat. No. 4,149,405 (Ringrose); U.S. Pat. No. 4,302,965 (Johnson et al.); U.S. Pat. No. 4,426,878 (Price et al.); U.S. Pat. No. 4,432,761 (Dawe); U.S. Pat. No. 4,616,503 (Plungis et al.); U.S. Pat. No. 4,637,250 (Irvine, Jr. et al.); U.S. Pat. No. 4,680,957 (Dodd); U.S. Pat. No. 4,680,958 (Ruelle et al.); U.S. Pat. No. 4,750,351 (Ball); U.S. Pat. No. 4,856,322 (Langrick et al.); U.S. Pat. No. 4,899,575 (Chu et al.); U.S. Pat. No. 5,142,899 (Park et al.); U.S. Pat. No. 5,222,497 (Ono); U.S. Pat. No. 5,224,375 (You et al.); U.S. Pat. No. 5,257,529 (Taniguchi et al.); U.S. Pat. No. 5,327,778 (Park); and U.S. Pat. No. 5,365,776 (Lehmann et al.).
The following U.S. patents disclose viscosity or flow measuring devices, or liquid level detecting devices using optical monitoring: U.S. Pat. No. 3,908,441 (Virloget); U.S. Pat. No. 5,099,698 (Kath, et. al.); U.S. Pat. No. 5,333,497 (Br nd Dag A. et al.). The Virloget ""441 patent discloses a device for use in viscometer that detects the level of a liquid in a transparent tube using photodetection. The Kath ""698 patent discloses an apparatus for optically scanning a rotameter flow gauge and determining the position of a float therein. The Br nd Dag A. ""497 patent discloses a method and apparatus for continuous measurement of liquid flow velocity of two risers by a charge coupled device (CCD) sensor.
U.S. Pat. No. 5,421,328 (Bedingham) discloses an intravascular blood parameter sensing system.
A statutory invention registration, H93 (Matta et al.) discloses an apparatus and method for measuring elongational viscosity of a test fluid using a movie or video camera to monitor a drop of the fluid under test.
The following publications discuss red blood cell deformability and/or devices used for determining such: Measurement of Human Red Blood Cell Deformability Using a Single Micropore on a Thin Si3N4 Film, by Ogura et al, IEEE Transactions on Biomedical Engineering, Vol. 38, No. 8, August 1991; the Pall BPF4 High Efficiency Leukocyte Removal Blood Processing Filter System, Pall Biomedical Products Corporation, 1993.
A device called the xe2x80x9cHevimet 40xe2x80x9d has recently been advertised at www.hevimet.freeserve.co.uk. The Hevimet 40 device is stated to be a whole blood and plasma viscometer that tracks the meniscus of a blood sample that falls due to gravity through a capillary. While the Hevimet 40 device may be generally suitable for some whole blood or blood plasma viscosity determinations, it appears to exhibit several significant drawbacks. For example, among other things, the Hevimet 40 device appears to require the use of anti-coagulants. Moreover, this device relies on the assumption that the circulatory characteristics of the blood sample are for a period of 3 hours the same as that for the patient""s circulating blood. That assumption may not be completely valid.
Notwithstanding the existence of the foregoing technology, a need remains for an apparatus and method for obtaining the viscosity of the blood of a living being in-vivo and over a range of shears and for the provision of such data in a short time span.
Accordingly, it is the general object of the instant invention to provide an apparatus and methods for meeting that need.
It is a further object of this invention to provide viscosity measuring an apparatus and methods for determining the viscosity of circulating blood over a range of shear rates, especially at low shear rates.
It is still yet a further object of this invention to provide an apparatus and methods for determining viscosity of the circulating blood of a living being (e.g., in-vivo blood viscosity measurement) without the need to directly measure pressure, flow and volume.
It is yet another object of this invention to provide an indication of the viscosity of the circulating blood of a living being in a short span of time.
It is yet another object of this invention to provide an apparatus and methods for measuring the viscosity of the circulating blood of a living being and with minimal invasiveness.
It is still yet another object of the present invention to provide an apparatus and methods for measuring the viscosity of the circulating blood of a living being that does not require the use of anti-coagulants, or other chemicals or biologically active materials.
It is still yet even another object of the present invention to provide an apparatus and method for measuring the viscosity of blood of a living being that does not require the blood to be exposed to atmosphere or oxygen.
It is still yet another object of the present invention to provide an apparatus and method for determining the viscosity of the circulating blood contemporaneous with the diversion of the blood into a conveying means (e.g., needle) when that means is coupled to, e.g., inserted into, the patient.
It is still yet another object of the present invention to provide an apparatus and methods for measuring the circulating blood viscosity of a living being that comprises disposable portions for maintaining a sterile environment, ease of use and repeat testing.
It is still yet another object of the present invention to provide a blood viscosity measuring apparatus and methods for determining the thixotropic point of the blood.
It is even yet another object of the present invention to provide an apparatus and methods for determining the yield stress of the circulating blood.
It is moreover another object of the present invention to provide an apparatus and methods for detecting circulating blood viscosity to evaluate the efficacy of pharmaceuticals, etc., to alter blood viscosity of the circulating blood of a living being.
It is even yet another object of this invention to provide an apparatus and methods for detecting the viscosity of the circulating blood of a patient while negating the effects of venous pressure.
In accordance with one aspect of this invention an apparatus is provided for effecting the viscosity measurement (e.g., in real-time) of circulating blood in a living being. The apparatus comprises: a lumen arranged to be coupled to the vascular system of the being; a pair of tubes having respective first ends coupled to the lumen for receipt of circulating blood from the being, and wherein one of the pair of tubes comprises a capillary tube having some known parameters; a valve for controlling the flow of circulating blood from the being""s vascular system to the pair of tubes; and an analyzer, coupled to the valve, for controlling the valve to permit the flow of blood into the pair of tubes whereupon the blood in each of the pair of tubes assumes a respective initial position with respect thereto. The analyzer is also arranged for operating the valve to isolate the pair of tubes from the being""s vascular system and for coupling the pair of tubes together so that the position of the blood in the pair of tubes changes. The analyzer is also arranged for monitoring the blood position change in one of the tubes and detecting a single blood position in the other one of the pair of tubes and calculating the viscosity based thereon.
In accordance with another aspect of this invention a method is provided for determining the viscosity (e.g., in real-time) of circulating blood of a living being. The method comprises the steps of: (a) providing access to the circulating blood of the living being to establish an input flow of circulating blood; (b) dividing the input flow of circulating blood into a first flow path and a second flow path into which respective portions of the input flow pass and wherein one of the first or second flow paths includes a passageway portion having some known parameters; (c) isolating the first and second flow paths from the input flow and coupling the first and second flow paths together so that the position of the blood in each of the flow paths changes; (d) monitoring the blood position change in one of the first and second flow paths over time; (e) detecting as single blood position in the other one of said first and second flow paths; and (f) calculating the viscosity of the circulating blood based on the blood position change, the single blood position and on selected known parameters of the passageway portion.
In accordance with still another aspect of this invention an apparatus is provided for effecting the viscosity measurement (e.g., in real-time) of circulating blood in a living being. The apparatus comprises: a lumen arranged to be coupled to the vascular system of the being; a pair of tubes having respective first ends and second ends wherein the first ends are coupled together via a capillary tube having some known parameters; a valve for controlling the flow of circulating blood from the being""s vascular system to the pair of tubes wherein the valve is coupled to a second end of one of the pair of tubes and is coupled to the lumen; and an analyzer, coupled to the valve, for controlling the valve to permit the flow of blood into the pair of tubes whereupon the blood in each of the pair of tubes assumes a respective initial position with respect thereto. The analyzer also is arranged for operating the valve to isolate the pair of tubes from the being""s vascular system so that the position of the blood in the pair of tubes changes. The analyzer also is arranged for monitoring the blood position change in one of the tubes and detecting a single blood position in the other one of the pair of tubes and calculating the viscosity of the blood based thereon.
In accordance with yet another aspect of this invention a method is provided for determining the viscosity (e.g., in real-time) of circulating blood of a living being. The method comprises the steps of: (a) providing access to the circulating blood of the living being to form an input flow of circulating blood; (b) directing the input flow into one end of a pair of tubes coupled together via a passageway having some known parameters whereby the input flow passes through a first one of the pair of tubes, through the passageway and into a first portion of a second one of the pair of tubes in order to form respective columns in the first and second tubes; (c) isolating the respective columns from the input flow so that the position of the blood in each of the columns changes; (d) monitoring the blood position change in one of the columns of blood over time; (e) detecting a single blood position in the other one of the pair of tubes; and (f) calculating the viscosity of the circulating blood based on the blood position change, the single blood position and on selected known parameters of the passageway.